Narcissus alkaloids (pretazettine & pseudolycorine) possess superior therapeutic effect on advanced Rauscher leukemia (as a model of human myelogenous leukemia) in comparison with most of the standard anticancer drugs, interferon inducers (Poly I:C and tilorone), immunostimulator (levamisole) or reverse transcriptase inhibitors (rifamycin SV and ethidium Br.). Especially, pretazettine (PTZ) is also active against spontaneous AKR leukemia (as a model of human T-lymphocytic leukemia) and has definite or marginal anticancer activity against non-viral transplantable tumors B16 melanoma and P388 leukemia). PTZ has no adverse effects on natural defense mechanisms by the long-term administration of the antiviral dose which decreases the viremia in leukemia mice. PTZ is an inhibitor of protein synthesis and reverse transcriptase. The toxicity in cats is reversible and not cumulative. Recently, in the ip-implanted Lewis lung tumor system, PTZ demonstrated therapeutically synergistic or additive effects in combination with standard drugs such as adriamycin, BCNU, cyclophosphamide, actinomycin-D, 5-FU, 6-thioguanine, methotrexate, and cis-platinum. The proposed project is the further basic studies of the alkaloid necessary before the possible clinical application, and include: 1) Studies of therapeutic effect of PTZ on spontaneous leukemia in AKR mice as a model of human T-lymphocytic leukemia, especially focused on the remission-maintenance therapy with PTZ after the remission-induction by standard drugs. 2) Studies of therapeutic effect of PTZ on Lewis lung carcinoma in mice as a model of human metastatic solid tumor after removing the primary Lewis tumor by surgery or making the lung-metastasis by iv injection of tumor cells. The potential of PTZ as an adjuvant agent in combination chemotherapy with standard drugs will also be evaluated in the Lewis sc- or ip-lung tumor system.